This application has related subject matter to that of the copending U.S. application Ser. No. 822,641 filed Jan. 27, 1986. It also has subject matter related to the U.S. copending application Ser. No. 044,358 filed Apr. 30, 1987, and copending application Ser. No. 058,393 entitled "Screw Conveyor Coupling Apparatus" and filed the same date as this application by the Assignee of the present invention.
As will be appreciated by those skilled in the art, specialized helical shaped devices such as screw conveyors are well known for the transport of various types of bulk material. Such conveyors generally include a helical shaped member which rotates within a housing or trough such that rotation of the screw conveyor along its longitudinal or central axis results in movement of the bulk material along the length of the device. In the past, such conveyors were typically constructed from metal, and each conveyor was specifically designed for a particular purpose and of a particular length. However, although most prior art conveyors were specifically designed to meet a particular application, there have been some attempts of providing a modular type conveyor of metal and wood. Examples of U.S. Patents which disclose such modular conveyors include U.S. Pat. No. 349,233 issued to James Nelson on Sept. 10, 1886; U.S. Pat. No. 455,384 issued to H. Binkholz on July 7, 1891; U.S. Pat. No. 525,194 issued to J. Dyson, et al on Aug. 20, 1894; U.S. Pat. No. 546,879 issued to J. Dyson, et al on Sept. 14, 1895; U.S. Pat. No. 1,867,573 issued to D. G. Leach on July 19, 1932; U.S. Pat. No. 2,492,915 issued to A. B. Carlson on Dec. 27, 1949; U.S. Pat. No. 3,648,826 issued to Dean P. Brooks on Mar. 14, 1972 and U.S. Pat. No. 3,705,644 issued to Claude E. Kawchitch on Dec. 12, 1972. However, a study of the above patents indicates that only the two Dyson, et al patents, the Nelson patent and the Kawchitch patent can be considered sectional or modular. In addition, the assignee of the present application filed an application for Letters Patent on Sept. 29, 1983 for a "Modular Screw Conveyor" and which has Ser. No. 537,345, and on Apr. 4, 1984 filed an application for "Mold and Process for Manufacturing Helical Shaped Items" which has Ser. No. 598,374.
As will be appreciated, one of the advantages of a plastic screw conveyor is its ease of cleaning, etc. due to the smooth and non-interrupted surfaces. Also, of course, it will be appreciated that by avoiding nuts and bolts which penetrate through the plastic screw conveyor and drive shaft, the conveying apparatus can be kept clean and free of debris, and corrosion of the drive shaft substantially prevented. In addition, for certain U.S.D.A. applications the screw conveyor apparatus must be sealed so as to eliminate any cavities etc. which might harbor bacteria. For such applications, a unitary drive shaft was normally necessary no matter how long the screw conveyor, since shaft couplings available at that time which used sleeves and bolts were unacceptable and would not provide the uninterrupted and crevice-free surfaces.
However, since many screw conveyor applications must operate over a wide range of temperatures, it has been discovered that the different coefficients of exposition of the metal drive shaft and the plastic screw conveyor may cause serious operational problems in such applications. In addition, the problems become even more serious in those applications which must meet U.S.D.A. strict requirements.
Therefore, it is an object of the present invention to provide screw conveyor apparatus which can operate satisfactoritly over a wide variation of temperatures.
It is another object of the present invention to provide a screw conveyor apparatus which can operate over a wide variation of temperatures while maintaining the metal drive shaft in a sealed and protected condition with respect to the exterior of the screw conveyor apparatus.
It is yet another object to provide a screw conveyor apparatus suitable for use over a wide variation of temperatures which is inexpensive and easy to manufacture.